1. Field of the Invention
The present invention is directed towards apparatus and methods for monitoring pressure within a patient's urethra. The present invention provides an intraurethral pressure monitor probe which may be used to monitor external pressure applied against the patient's urethra, particularly during a surgical procedure to correct urinary incontinence.
2. Description of Related Art
Female stress urinary incontinence ("SUI"), defined as the unintentional loss of urine, is a common problem after vaginal childbirth. In women afflicted with this problem, the incontinence usually occurs during coughing, sneezing, or physical activity. While effective surgical treatment for this condition has existed for many decades, the procedures typically involve major abdominal surgery with accompanying post-operative limitations lasting six to eight weeks. Because of the nature of some of the currently-employed surgical procedures and the risks associated therewith, many women simply resort to diaper-like incontinence pads, or simply avoid any activities which may result in the unintentional loss of urine.
Continence generally requires proper functioning of the bladder and the intrinsic sphincter muscle which surrounds the urethra, as well as the proper anatomical relationship between the bladder, the urethra and other abdominal structures. In the normal resting state, the closure force provided by the intrinsic sphincter, as well as external pressure exerted on the collapsible urethra by the surrounding musculature, both provide sufficient force to overcome bladder pressure, thereby maintaining continence. During moments of coughing, sneezing, or other physical activities, greater pressure will be exerted on the dome of a filled bladder. In women not afflicted with SUI, the increased intra-abdominal pressure is also transmitted to the urethra, and this increased external pressure on the urethra acts to prevent the unwanted loss of urine. Sufferers of SUI, however, are not so fortunate.
SUI is generally caused by two anatomic etiologies: intrinsic sphincter deficiency ("ISD"); and a loss of support of the periurethral tissue at the urethra-vesicular junction ("UVJ"--the region where the urethra enters the bladder). The latter situation (also known as hypermobile bladder neck) often occurs after vaginal childbirth, and is caused by the separation of the connective tissue which secures the periurethral tissue to the underside of the pubic bone. When this occurs, the UVJ will sag into the vagina, thereby reducing transmission of intra-abdominal pressure to the urethra during moments of stress (such as coughing or laughing). ISD, on the other hand, is a functional problem in that the urethral sphincter does not respond to sudden increases in intra-abdominal pressure. ISD can be caused by muscular withering with age, arterial sclerosis, diabetes, or prior incontinence surgery, all of which are related to a compromised blood supply to the detrusor muscle surrounding the urethra.
For both types of stress urinary incontinence, various types of surgical procedures have been developed which often provide relief. "Urethropexy" procedures suspend a portion of the tissue adjacent to the patient's urethra (also referred to as the periurethral tissue) relative to a structure within the patient's body by means of a fixation device (such as sutures). In one common procedure, the results of which are depicted in FIG. 3 herein, sutures are secured between the periurethral tissue on either side of the urethra and an anatomical structure located above the urethra. Typically, the sutures are secured between the periurethral tissue and the pubic bone (either using bone anchors or by suturing directly to the periosteum of the pubic bone), Cooper's ligament, or the abdominal fascia. The sutures pull the vaginal wall and periurethral tissue upwardly towards the urethra, which in turn provides an upward force on the urethra (indicated by the arrows in FIG. 3). This upward force acts to restore the urethra to the desired elevation or angle, thereby allowing increases in intra-abdominal pressure to be transmitted to the urethra (as an external force). Such procedures are described, for example, in U.S. Pat. Nos. 5,591,163, 5,643,288, 5,662,654 and 5,697,931, all of which are incorporated herein by reference.
Another type of urethropexy procedure often employed is referred to as a "sling procedure." A sling procedure is particularly recommended when the incontinence is caused by ISD or when the support tissues at the bladder neck (i.e., UVJ) are irreparably damaged. In the sling procedure (also known as a pubovaginal or suburethral sling procedure), a strip of flexible material (i.e., the sling) is positioned beneath the urethra, and its two ends are suspended from an anatomical support structure. Typically, the width of the sling is such that it extends from the UVJ to at least the midpoint of the urethra. As seen in FIG. 2 herein, the sling is employed to both lift and support the urethra in order to provide continence. The urethra is elevated and is supported underneath by the sling. The sling also applies an upward closure pressure on the urethra, thereby alleviating any portion of the incontinence caused by intrinsic sphincter deficiency. The sling may be attached either directly to a supporting structure, (such as the abdominal fascia) or by means of another fixation device such as one or more sutures. Typically, the sling is sutured to the pubic bone (either by way of bone anchors or suturing directly to the periosteum), Cooper's ligament or abdominal fascia. An exemplary sling procedure, as well as apparatus for use in such procedure, is described in further detail in application Ser. No. 08/818,391, filed on Mar. 14, 1997, pending which is incorporated herein by reference.
In the sling procedure, the sling itself must be positioned beneath the urethra such that it can be employed to provide an upward force to elevate the urethra. Therefore, the sling must be positioned beneath the vaginal mucosa, typically so that it is located between the vaginal mucosa (i.e., the vaginal wall) and the periurethral fascia located directly beneath the urethra. This generally requires that the surgeon create a vaginal skin flap by peeling a portion of the vaginal mucosa away from the fascia located beneath the urethra (also referred to as the pubocervical fascia).
In either of the above-described procedures for treating incontinence by elevating the patient's urethra, the upper force provided by the fixation device (e.g., the sutures or the sling) must be sufficient to provide continence, while not being so great that the patient is unable to urinate. Thus, the surgeon would prefer a method of determining the amount of pressure applied against the urethra while the procedure is being performed, thereby ensuring that the sutures (FIG. 3) or sling (FIG. 2) provide the proper upward force. It must be kept in mind, however, that the force provided by the existing structures within the patient, including the intrinsic sphincter, must be taken into account. For example, if the patient suffers from hypermobile bladder neck as well as intrinsic sphincter deficiency, the degree of elevation which will correspond to the pressure imparted by the sling will need to be greater than if the patient only suffers from hypermobile bladder neck. Therefore, there is a need for a pressure monitoring device which will monitor intraurethral pressures while the incontinence procedure is being performed. As used herein, the term "intraurethral pressure" simply refers to the external pressure applied against the urethra, and includes the force imparted by the intrinsic sphincter, as well as the tissue and musculature surrounding the urethra. The pressure monitoring device should also be configured so as to isolate the urethra from the bladder, thereby ensuring that internal bladder pressure does not influence the pressure reading obtained.
Although numerous types of pressure monitoring devices have been developed for measuring pressures within body cavities, including the urethra, none of these prior art apparatus can be effectively employed during a surgical procedure to correct incontinence. Two of the more significant drawbacks associated with existing pressure monitoring devices is that most do not provide an effective means of eliminating the influence of bladder pressure. In addition, it is often difficult, if not impossible, to ensure that the pressure responsive region of the monitor is positioned at the proper location within the urethra. This is particularly problematic when the pressure monitor is positioned within the urethra while the procedure is being performed. As the urethra is elevated by means of the sutures and/or the sling, pressure monitoring devices of the prior art will not remain in the proper location within the urethra. Furthermore, any type of rigid probe extending through the entire length of the urethra will also interfere with proper restoration of the urethral angle. Therefore, there is a need for an intraurethral pressure monitor probe which overcomes these deficiencies of the prior art.